Damper systems which can be adjusted actively for vehicles are known, which damper systems as a rule operate according to the principle of a variable opening cross section. Dampers of this type set the corresponding shock absorber characteristic values via hydraulic proportional valves and can be adapted to different driving situations, for example with regard to the roadway surface or to different client requests. With the aid of a movable slide which is moved by a magnet coil, the proportional valves continuously control the throughflow of fluid in the damper. Depending on the application of current to the electromagnetic proportional valve, the cross section thereof through which oil flows is changed. This brings about a change in the pressure loss which should have a declining profile as the throughflow increases. For this purpose, the resulting flow forces on the valve slide which changes the cross section have to be kept as small as possible in the opening direction, since otherwise the valve slide does not open sufficient cross section and, as a result, the pressure loss has an increasing profile as the volumetric flow rises.
A proportional valve which forms the generic type is known, for example, from DE 10 2007 005 466 A1, the valve slide of which proportional valve is connected directly to a magnet armature for the electromagnetic actuation of the valve. The cross section of a passage in the housing, which passage connects the valve inlet to a valve outlet, is changed continuously by way of a control edge which is provided on the valve slide. In this proportional valve, the valve slide is configured as an outer slide and is mounted and guided on a tubular slide guide which is fastened in the valve housing on the inlet side. Said valve slide is therefore mounted firstly via the magnet armature and secondly via said tubular slide guide. As a result of this double mounting of the valve slide, the involved components have to meet high manufacturing accuracies which likewise lead to high manufacturing costs.
In the known electromagnetic fluid valves, a multiplicity of radial inlet openings are frequently provided in the housing. The pressure medium is guided through said radial inlet openings into the interior of the housing of the electromagnetic fluid valve and is guided there via a channel to at least one outlet opening. Regulation of the throughflow of the pressure medium takes place via a suitable movable slide, by the movable slide closing the inlet openings to a greater or lesser extent and thus throttling the pressure medium in the channel.
It is problematical in the use of a multiplicity of radial inlet openings that the pressure medium in the interior of the housing of the electromagnetic fluid valve flows toward itself and this leads to eddying there. An unstable flow state of this type, that is to say a change from turbulent to laminar flow in valves, through which fluid flows, is problematical because fluctuating flow forces are produced as a result.
The invention has the aim of avoiding or at least reducing fluctuating flow forces of this type and of ensuring from the start that only a laminar flow of the pressure medium takes place into the housing of the electromagnetic fluid valve.